Fooled into coming overseas by news of his mother's imminent death, high school student Kaido Haru encounters a boy who insists that he's his brother. Haru does his best to raise feral and obstinate Ren, but there seems to be a secret behind Ren's birth. On top of that, just when Ren begins to warm up to Haru, tragedy strikes. Five years later, Haru reunites with Ren, all grown up in Tokyo, but…